Emergency buoyancy system

ABSTRACT

Gases from a solid propellent rocket fuel unit are mixed with carbon dioxide from a pressure vessel to inflate an inflatable buoy, which is connected to a riser pipe utilized in drilling a hole in the bottom of the ocean. The structure buoy is fastened to the riser pipe, about 300 feet below the water, at a level unaffected by wave action, but accessible to divers and is adapted to be rapidly inflated to support the riser pipe, if there is a severe storm and it becomes necessary to cut the drilling platform loose from the riser pipe.

United States Patent Patterson, Jr. et al.

[451 Mar. 26, 1974 EMERGENCY BUOYANCY SYSTEM 3,566,426 3/1971 Davidsonet a1. 9/9

[75] Inventors: Arthur E. Patterson, Jr., Cupertino;

Edward J. Barakauskas, Saratoga, Pmrary Emm" 1er Duane Reger both ofCalif Asszstant Exammer-Jesus D. Sotelo Attorney, Agent, or FirmF. J.Baehr, Jr. [73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, 57 ABSTRACT [22 Filed: Oct. 14, 1971 Gases from a solidpropellent rocket fuel unit are mixed with carbon dioxide from apressure vessel to 7 189383 inflate an inflatable buoy, which isconnected to a riser pipe utilized in drilling a hole in the bottom of[52] U.S. Cl ll4/0.5 D the ocean. The structure buoy is fastened to theriser [51] Int. Cl B63b 35/44 pipe, about 300 feet below the water, at alevel unaf- [58] Field of Search 114/.5 R, .5 D, 16.4, 16.5, fected bywave action, but accessible to divers and is 114/166, 16.7, 16.8; 9/8 R,8.3 E, 9 adapted to be rapidly inflated to support the riser pipe, ifthere is a severe storm and it becomes neces- [56] References Cited saryto cut the drilling platform loose from the riser UNITED STATES PATENTSP P 3,210,785 10/1965 Ward 9/9 3 Claims, 4 Drawing Figures e a II IIEMERGENCY BUOYANCY SYSTEM The invention hereinafter described was madein the course of, or under a contract for, the National ScienceFoundation, an agency of the U.S. Government.

BACKGROUND OF THE INVENTION This invention relates to deep waterdrilling and more particularly to an emergency buoyancy system forsupporting the riser casing if the drilling platform must be cut loosefrom the hole.

Development of offshore drilling began in the 1930s and developedsimultaneously in California and Louisiana, however the early drillingplatforms, which support the familiar oil derricks, were either onartificial islands or supported by legs extended to the bottom of thesea. By the mid l950s floating platforms with legs that were jacked tothe bottom to raise the platform above the water came into use alongwith floating platforms, which were held in place by mooring linesfastened to buoys anchored to the floor of the sea. The latterarrangement could be utilized to drill holes under water several hundredfeet deep. In 1961 the first deep sea holes were drilled in water over10,000 feet deep, demonstrating the feasibility of dynamicallypositioning a drilling platform in the ocean. For additional infomiationon the development of deep sea drilling, reference may be made to A HoleIn The Bottom Of The Sea by Willard Bascom, published in 1961, whichrelates to the story of the Mohole Project.

SUMMARY OF THE INVENTION In general, an emergency buoyancy system madein accordance with this invention comprises a tank for containingpressurized fluid, an exothermic gas generator, a mixing chamber formixing fluid from the tank with gas produced by the gas generator toform a gaseous mixture and an inflatable buoy adapted to contain thegaseous mixture and provide a predetermined amount of buoyancy.

BRIEF DESCRIPTION OF THE DRAWINGS The objects and advantages of thisinvention will be come more apparent from reading the following detaileddescription in connection with the accompanying drawings, in which:

FIG. 1 is a partial elevational view of a floating drilling platform andan emergency buoyancy system made in accordance with this invention;

FIG. 2 is an enlarged sectional view taken on line ll-II of FIG. 1;

FIG. 3 is an enlarged sectional view taken on line III- -III of FIG. 2;and

FIG. 4 is an enlarged sectional view of a quick opening valve and mixingchamber made in accordance with this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings indetail, FIG. 1 shows a floating drilling platform 1 having a derrick 3disposed thereon and a riser pipeor casing 5 depending from the drillingplatform 1. A drill pipe or drill string 7 having a boring bit at thelower end thereof extends downwardly through the casing to bore a holebeneath the floor of the ocean in several thousand feet of water. In theevent of a severe storm it may be necessary to detach the drillingplatform 1 from the riser pipe 5. With the drilling platform removed,additional buoyancy may be required to support the riser pipe. Theamount of buoyancy would vary depending on the length of the riser pipe,its size, the desired tension, and many other factors. The additionalbuoyancy is preferably added at a level not appreciably affected by waveaction and yet accessible to divers.

As shown in FIG. 1, an emergency buoyancy system 8 adapted to providegases to an inflatable buoy 9 is disposed approximately 300 feet belowthe water level. Utilizing compressed gases to inflate the buoy wouldproduce undesirably low temperatures, which could cause freezing andmalfunction of the system 8, while utilizing a gas generator, such as asolid propellent fuel unit, would produce a large quantity of compressedgases at elevated temperatures, which are difficult to handle and wouldcool over a period of time, reducing the buoyancy. Therefore a workablesystem must produce gases at the ambient pressure and temperature at adepth of 300 feet below the surface of water.

As shown in FIGS. 2 and 3, such an emergency buoyancy system comprises aC0 tank or pressure vessel 11, an exothermic gas generator 13 having asolid fuel rocket propellent unit 14, commercially known as a Jato unit(jet assist take-off unit as manufactured by Hercules PowderCorporation, Radford, Va.), disposed therein and a combination quickopening valve and mixing chamber 15 adapted to mix the CO fluid with thegaseous products of combustion from the gas generator l3 tempering bothfluids so that the gaseous mixture has a temperature of approximately Fas it enters the inflatable buoy 9, which is fastened to the riser pipe5 at a depth of approximately 300 feet below the surface of the water.

Each CO tank 11 and gas generator 13 will produce a predetermined amountof buoyancy so that by providing the proper size inflatable buoys 9 anda plurality of CO tanks 11 and gas generators 13, the amount of buoyancycan be varied in increments providing a flexible system capable ofresponding to various buoyancy needs.

An ignition control system which monitors the amount of CO in each tank11 and provides an ignition system for each gas generator 13 is operablefrom the drilling platform 1 above the water, and contains monitorswhich inform the operator that the system has functioned.

As shown in FIGS. 2 and 3, each CO tank 11 and gas generator 13 iscooperatively associated with a mixing chamber 15, which is connected tothe inflatable buoy 9 by a manifold 17. As will be hereinafter describedin detail, the tank 11, gas generator 13 and mixing chamber 15 areremovably fastened to the manifold 17 and riser pipe 5 so that afterthey have functioned, they can be easily removed and recharged, andsubsequently reinstalled to provide buoyancy in future emergencies.

As shown in FIG. 4, the combination quick opening valve and mixingchamber 15 comprises an outer cylindrical shell or tubular housing 19disposed generally horizontally, an inlet port 21 in communication withthe CO tank 11 and a cylindrical or tubular sleeve member 23 disposedwithin the outer cylindrical shell 19. The sleeve member 23 is axiallyaligned with the outer shell 19 and is flange mounted to one endthereof. The flanged end 25 of the sleeve member 23 has an orifice 27disposed therein for receiving the discharge end of the Jato unit 14 anda seal 29 disposed to seal one end of the annular chamber 31 formedbetween the shell 19 and sleeve 23. An annular seal ring 33 is sealwelded to the shell 19 and has a circumferential groove 35 adapted toreceive an O-ring type seal 37, which engages the outer peripheralsurface of the sleeve 23 to seal the other end of the chamber 31. Aplurality of openings or ports 39 are circumferentially spaced adjacentthe central portion of the sleeve placing the annular chamber 31 intocommunication with the bore or inner surface of the sleeve 23.

A spool shaped valve member 41 is slidably disposed within the sleeve23. The spool member 41 has end flanges 43, which slidably engage theinner surface of the sleeve 23 and each flange 43 has a groove 45 shapedto receive an O-ring 47, which forms a seal at the end flanges 43. Thespool member 41 is so disposed with respect to the ports 39 as to form aseal on opposite sides thereof closing or plugging off the ports 39. Asmall diameter lock wire 49 is fastened to the spool member 41 and tothe sleeve member 23 limiting relative movement therebetween. The lockwire 49 is sufficiently strong to hold the spool member 41 in pluggingrelation with the ports 39 under severe operating conditions, however,the lock wire 49 is designed to break when subjected to the pressureproduced by the gas generator 13 when it is ignited. A counter-boreforms a step 50 in the inner surface of the sleeve forming aunidirectional valve, which only responds to a pressure build-up on oneside thereof.

The other end of the shell 19 is closed by a cupshaped cap 51 having anouter flange 53, which is fastened to an inwardly directed flange 55 atthe end of the shell forming a seal therebetween. The cap 51 is of theproper diameter and depth of receive the spool member 41 and has aplurality of fingers 57 extending outwardly to the sleeve 23. Thefingers 57 have tip ends, which taper outwardly to provide a guidewayfor receiving the spool member 41 as it leaves the sleeve 23, to assistin directing the spool member 41 towards the cup-shaped cap 51, when thegas generator 13 is ignited.

A discharge port 58 is disposed in the shell 19 adjacent the fingers 57.A short nozzle 59 connects the discharge port 57 to the manifold 17.Quick disconnecting mating flanges 61 are provided and are held insealing relation by a quick disconnect clamp 62. A portion of thedischarge nozzle 59 extends downwardly into the manifold, the lower endof the discharge nozzle 59 is tapered inwardly to assist in aligning theflanges 61 so that they can be assembled under water.

As shown in FIG. 4, the inlet port 21 is placed in communication withthe CO tank 11 by a short nozzle 13 welded to the tank 11 and to theshell 19. FIG. 4 also shows the Jato unit 14 mounted in the gasgenerator 13, which comprises a tubular shell portion 67 having aflanged end closure 69. The Jato unit 14 is suspended from mountingbrackets 71 and 73 fastened to the shell portion 67. The mountingbrackets locate the Jato unit 14 within the shell so that the dischargenozzle extends through the orifice 27 and withstand the thrust of theJato unit 14 after it is ignited. The mounting bracket 71 is formed frominterconnecting portions 75 and 77 which are bolted together to fix theposition of the Jato unit 14 within the shell 67 and allow it to beeasily replaced.

The CO; tank 11, gas generator 13, and mixing chamber 15 are fastenedtogether to form a unitized structure or assembly, which is supportedfrom a pair of collars 79 and 81 fastened to the riser pipe 5. The uppercollar 79 has a pair of semicircular plates 83 extending radiallytherefrom. The plates 83 have arcuate scalloped peripheral edges forreceiving the CO tanks 11 and a plurality of holes 85 adapted to receivea tapered pin 87, which is fastened to the upper end of the CO, tank 11by a bracket 89. The lower collar 81 is encircled by an l-beam 91, whichis fastened thereto by a plurality of struts 93 extending radiallyoutwardly from the lower collar 81. The l-beam 91 is disposed under theflanges of the end closures 69 and has a pair of wedge-shaped blocks 95fastened thereto to form a cradle for each gas generator. The CO tanks11 and gas generators 13 have lifting lugs 97 and 99, respectively,properly disposed so that when the quick disconnect flange clamp 62 isremoved the assembly can be removed from the manifold 17. An isolationvalve 102 is disposed in the manifold upstream of the inflatable buoy sothat portions thereof may be shut off.

Each CO tank 11 and gas generator 13 will produce a predetermined amountof buoyancy so that by varying the number of units activated incrementalbuoyancies can be obtained. To activate a portion of the system a Jatounit 14 is ignited by operating a switch at the surface to commenceburning of the solid fuel propellent. The products of combustion aregases so that the pressure in the shell 67 of the gas generator 13builds up rapidly causing the lock wire 49 holding the spool valve 41 inplace to break, allowing the valve member 41 to slide into thecup-shaped cap 51, and liquid CO to begin to flow through the ports 39and into the mixing chamber 15, wherein it vaporizes and mixes with theproducts of combustion from the Jato unit 14 to reduce the temperatureof the products of combustion and raise the temperature of the CO sothat the temperature of the mixture leaving the discharge port 57 isapproximately F, which is generally equal to the temperature of thewater at a depth of 300 feet. Once the Jato unit 14 is ignited it burnswithout external oxygen until it is burned out. The CO; tank is sized toprovide sufficient cooling for the Jato unit. The CO begins to flow intothe mixing chamber shortly after combustion of the Jato unit 14 isinitiated and continues to flow during combustion and for a short periodafter combustion is completed to insure that no hot gases flow throughthe manifold and into the inflatable buoy 9. As noted hereinbefore, thespool valve 41 is unidirectional so that no other valving is required inthe manifold and activation of one unit will not cause spool valves ofother units to operate. Thus, the apparatus hereinbefore describedadvantageously produce incremental quantities of noncondensable gaseousmixtures at the ambient temperature and pressure expected to existapproximately 300 feet below the surface of the water to provideincremental amounts of emergency buoyancy.

What is claimed is:

1. An emergency buoyancy system comprising a pressure vessel forpressurized fluid; an exothermic gas generator; a mixing chamber fluidlyconnected to said pressure vessel and said gas generator for producing agaseous mixture of pressurized fluid from said pressure vessel and gasfrom said gas generator; said mixing chamber comprising an outer tubularshell, a sleeve disposed within the outer shell, the sleeve beingfastened to one end of said shell, a circumferential seal between theshell and the sleeve, the gas generator being disposed to discharge intosaid sleeve, a second circumferential seal between said sleeve and saidshell cooperating with said first mentioned circumferential seal to forman annular chamber between said sleeve and said shell, said shell havingan opening placing the pressure vessel in communication with saidannular chamber, said sleeve member having at least one port placingsaid annular chamber in communication with the inner side of saidsleeve, means for plugging said port, means for holding said pluggingmeans in plugging relation under normal conditions and operable to allowsaid plugging means to move out of plugging relationship oxide.

1. An emergency buoyancy system comprising a pressure vessel forpressurized fluid; an exothermic gas generator; a mixing chamber fluidlyconnected to said pressure vessel and said gas generator for producing agaseous mixture of pressurized fluid from said pressure vessel and gasfrom said gas generator; said mixing chamber comprising an outer tubularshell, a sleeve disposed within the outer shell, the sleeve beingfastened to one end of said shell, a circumferential seal between theshell and the sleeve, the gas generator being disposed to discharge intosaid sleeve, a second circumferential seal between said sleeve and saidshell cooperating with said first mentioned circumferential seal to forman annular chamber between said sleeve and said shell, said shell havingan opening placing the pressure vessel in communication with saidannular chamber, said sleeve member having at least one port placingsaid annular chamber in communication with the inner side of saidsleeve, means for plugging said port, means for holding said pluggingmeans in plugging relation under normal conditions and operable to allowsaid plugging means to move out of plugging relationship with said port,when said gas generator is activated, and an opening in said shell fordischarging the gaseous mixture from said shell at ambient temperature;and means for containing said gaseous mixture under water to provide apredetermined amount of buoyancy.
 2. An emergency buoyancy system as setforth in claim 1, wherein the plugging means is slidably disposed withinthe sleeve.
 3. An emergency buoyancy system as set forth in claim 1,wherein the gas generator comprises a Solid propellent rocket fuel andthe fluid is liquid carbon dioxide.